overheating kxf250

[overbore]

I read some other post after doing a search,but still asking

for opinions on the 04 kxf overheating problem.Its not mine and

posting to try and help someone else out.

I know he put another water pump on with more flow,

put bigger radiaters,and the little deflectors,and also

changed the pilot to a 42.

Still overheats when riding single track sections with a lot of

clutching.

someone told him since it overheated even once that he should

or had to change the base gasket,and I dont thing that he

changed the cap yet on the radiater as I saw on my searches.

I have always thought that it has something to do with him

changing the exhaust system before he ever rode it with a new

fmf powerbomb and q pipe which is causing to much restrictions.

Any and all suggestions welcome.

overbore. ?

[4strokesrule]

First of all if it is just pushing out some coolant it doesn't mean it is overheating. A 1.6 radiator cap and not filling the radiator to the lip of the fill cap will help.

You can also fabricate an overflow bottle from a White Rain pump hair spray bottle that will fit between plastic mud deflector on the lower left side of the frame and the engine case. Just trim the plastic deflector to allow the bottle to fit down in there and fasten with a plastic tie strap. Push the pump assy out of the cap of the spray bottle and insert the overflow tube from the radiator thru the cap and down to near the bottom of the bottle. Drill a hole near the top of the bottle on the side so another short length of hose fits tightly for a vent and overflow. This will allow excess coolant to be captured when the engine is hot and will be sucked back into the radiator as the engine cools on easier parts of the course. Or you can purchase a coolant tank for a KDX.

Usually a bike runs hotter when a LESS restrictive pipe is added if proper jetting is not maintained due to it running leaner. He could have a leaky head gasket, the base gasket would only make it leak oil on a 4 stroke. On a 2 stroke it would allow it to suck air and run lean = HOt.

Slipping the clutch does add alot of heat quickly. Use the right gear and let the torque do the rest. This ain't a 2 stroke, use the WIDE powerband.

[calidunes]

If he's bogging the engine a lot he will have similar problems.I know this may sound odd, but make sure the brakes aren't dragging severly. It's possible that some debris got caught between the rotor and the pads and is causing some serious drag to occur.

[raceridrrmz250]

hey 4strokesrule how does the coolant get sucked back up through the overflow tube. my mistake if i missed something.

[raceridrrmz250]

as your friend what kind of coolant he is using. When I bought my bike (04 rmz 250) it had engine ice in it and I went out my second ride and it overheated. wasn't even riding that long. but i asked the dealer about it and the one mechanic who used to race said that he had never had good results with engine ice and said to try something called water wetter. i think thats right. or just regular half and half. water and antifreeze. the water should be distilled. hope that helps. pm me if you have any more questions about overheating.

[overbore]

Thanks all that responded.First post here and joining and we appreciate the help.

Its great when people all help each other and we dont have to re invent the

wheel again.I found out yesterday after signing off that he already had put the

1.6 cap on also.I do remember when riding that he had to add some engine ice because it had thrown half of it out,so I know that what he had in it with a tablespoon of water wetter added also.Sounds like with the bigger pump,radiaters,

and the 1.6 it shouldnt be doing it,but I know it is.We ride some pretty technical

single track moving pretty slow alot of times,which doesnt help.I just cant believe

that kawasaki would sell something like this for off road.I know that it is a motocross

bike converted for the woods,but there has to be a fan or something to help when

your not moving much,like a car when you come to a stop light and the engine gets

to a temp then the computer turns on the fan.

overbore.

[calidunes]

This bike was designed for mx, not woods. However, many people use it for woods also. If the head gasket is no good, then this will continue to happen. Since you have done quite a few upgrades in order to help keep the bike cool, this would be my next guess.

[Rmzfastmxkid12]

i know on my 04 rmz250 since i just had 2 grand worth of motor work done to it i'm putting boyesen water pump, air tract system which james stewert and RC run on there bikes, plus i'll have custom drilled holes in the radiator guards and i'll use engine ice and water wetter also i'll have a 1.6 radiator cap now i havn't rode my bike because this is like a 3-4 month project but i do have 2 have it ready for this 05 race season in march but anyway you might want to try some of the stuff on my list but that is just a suggestion..

[fletch7276]

Overbore, I can add two suggestions.

1. Your motor is obviously dealing with a lot of friction, considering all the mods you made and your bike still gets hot. reducing clutch usage, or going to a kevlar clutch (something that dissipates heat better) would help.

2. You might just have some rough rings on your piston. bikes break in differently--I had a 97 CR that ran hot from day one. I dropped a new piston kit in it with a nice, long break in period and the bike ran considerably cooler. It ends up that the stock piston rings were pretty burred up (sharp edges).

Neither one of these mods would cost you more than $100 or so, and both are common maintenance items on a 250F anyway. good luck.

Rmzfastmxkid12, not to go on a tangent, but what motor work did you have done? and can you explain the air tract system? thats new to me.

[fletch7276]

oh, one last thing. Its expensive, but porting can make a world of difference as well for coolant flow. you might have some blockage, and some chambers that need de-burring. from my days of sending off 2-stroke cylinders to be ported, you would be amazed to see the debris that can exist in the coolant chambers.

[4strokesrule]

hey 4strokesrule how does the coolant get sucked back up through the overflow tube. my mistake if i missed something.

The same way it does in an automotive application, nearly every modern car and truck has a plastic resevoir in addition to the radiator. As the engine warms up and the coolant expands (city driving, Ac on, engine idleing at stop lights) the excess is forced past the cap into the resevoir. As the engine cools down (open road or faster driving conditions) the pressure drops and creates a partial vacuum pulling the coolant back into the radiator. Or it will at least happen when the engine is stopped and cools completely. Examine the radiator cap and you will find the small metal part in the center (on the very bottom as installed) will pull away from the cap with the minimum pressure of a finger nail under it. This passage seals as pressure builds but opens as the engine cools allowing the coolant to return.

I used our KX250f to pull a disabled Husky 410 out of the woods and the bottle I described earlier caught about 2" of overflow. When the bike cooled it was gone from the bottle and the radiator was full to the neck.

The owner might want to consider a KLX300 if this is the type riding he does most. They are awsome woods bikes with minimum mods and will run all day slow and never get hot.

[raceridrrmz250]

thanks I'll go check that out. I thought that it was strange that it would take that much pressuer to let out coolant. but could siphon it back in so easily. one way valve is what your saying I guess. thanks

[4strokesrule]

thanks I'll go check that out. I thought that it was strange that it would take that much pressuer to let out coolant. but could siphon it back in so easily. one way valve is what your saying I guess. thanks

You got it figured out.

[overbore]

well thanks again for all the responses.No one has said anything about the

exhaust.Since he changed it does anyone have the powerbomb and q pipe

to see if they also have the problem?I guess its time to tear apart for he says

he has to much money invested in it already and would loose a couple grand

trading again.Any ideals on exhaust or anything else.

overbore.

[4strokesrule]

Usually a bike runs hotter when a LESS restrictive pipe is added if proper jetting is not maintained due to it running leaner.

AHEM.

[MattFisher]

You may want to try this stuff: http://www.two2cool.com/

Although it goes in the tranny/motor, not the radiator, it does work very well at reducing engine temps. The KTM 50cc racers swear by it, and the clutches in those little monsters can hit 600 degrees.

[masterlink]

what is the air track system .masterlink

[binder929rr]

Check the spark plug to see if he's running lean. Putting higher flowing exhaust without re-jetting it will run lean, which means hot. Also, see what kind of water pump he has on it. I have a boysen and it works great, with engine ice. I've never had a problem with my bike yet. Also, how cold is it outside. I put a 180 main jet in my bike and that's with stock exhaust. He probably needs a bigger jet. Also, with engine ice, you said he put water wetter with it. This is incorrect. There is to be NOTHING added with engine ice to get the best performence out of it. I and all the racers I know run engine ice and have had great results with it.

I see a lot of woods riders using vented front number plates, vented front fenders, and drilling lots of small holes in their radiator guards. That will help with flow.

Like someone else said, if your head gasket is leaking, it will blow hot engine gasses into your coolant system which will cause it to run very hot.

It's just hard to think that this bike is going to over-heat with the large radiators and high flow pump without something internally wrong. I have seen many hare scramble racers with them and not have that many mods to their bikes and still not having over-heating problems.

I would try changing the gearing so you don't have to use the clutch as much. It's a 4 stroke.